I do think it matters a lot. If the Windows and Mac platforms are only accessible through App Stores then we, developers, will have to pay whatever royalty or percentage those companies see fit to charge. We may also lose the ability to publish software at all to those platforms if they so decide without much notice and maybe even without recourse.

Although we could pass the expense of the App Store or absorb the cost, I guess most software companies would go bankrupt if Microsoft or Apple cancelled their accounts.